1. Field of the Invention
The present invention relates to subsea structure flowline connection systems. More particularly, the present invention relates to systems whereby a fly-in connector is joined to subsea structures so as to establish a flow communication therewith. More particularly, the present invention relates to a flowline connector assembly for use with large bore connections, e.g. 2 inch and above bore connection, between the fly-in connector and the flowline connector.
2. Background
Flowlines are used to interconnect pieces of subsea oil-field equipment for fluid communication, i.e. hydrocarbons (oil/gas), injection fluids/gases or hydraulic fluid. They generally take the form of somewhat flexible armoured hoses or pipes, provided with subsea matable connectors at either end. Typically, they are installed by being lowered into place from a pipe-laying vessel, with the final positioning and make-up of the end connectors carried out by divers or by an ROV. Short ROV-installable hoses and pipes are used to interconnect adjacent pieces of subsea equipment.
Examples of subsea equipment that may be interconnected using flowlines include subsea Christmas trees, manifolds, pipeline end terminations (PLET), capping stacks, blowout preventors or any other subsea structures that require flowline or hydraulic connections. This equipment is typically located on the seabed.
When there are several different pieces of equipment to be interconnected, installation of the necessary pipes and flowlines can be time-consuming and difficult. An end of each flowline is generally lowered vertically to the seabed from a pipe-laying or installation vessel. The flowline is then laid out horizontally between the points to be interconnected. The flowline ends must then be retrieved from the seabed bed by an ROV. The end connectors are aligned with the subsea equipment for make-up of the required fluid-tight, i.e. liquid and/or gas tight, connections.
A known type of connector for the flowline has a first part mounted to a piece of subsea equipment as described earlier, such as a wellhead, and a mating second part fitted to the end of a flowline. In use, the second part is lowered towards the sea bed and is stabbed from above into the first. A pivot arrangement then guides the second part and attached flowline so as to hinge over into a generally horizontal position, in which the flowline may be laid away along the sea bed, and in which the connector first and second mating parts are axially aligned for make-up of a fluid-tight connection between them.
In order to connect various flowlines to the equipment on the ocean floor, special connectors known as “flying leads” are often employed. The flying leads connect the ends of flowlines to subsea equipment, such as connecting to a control pod on a manifold or subsea tree at one end to an umbilical termination assembly at the other end. In shallow water, flying leads are connected to subsea equipment by divers. In deeper waters, one or more remotely-operated vehicles (ROV) are utilized.
Different configurations of flying leads are presently available. Two types of flying leads for interconnecting the elements of a subsea production system are hydraulic flying leads or steel flying leads. Both types of leads may house lines for monitoring, control and, when necessary, chemical injection in the subsea system. Each type of lead has benefits and limitations.
The hydraulic flying leads commonly are made up of thermoplastic hoses of various sizes and configurations. In known arrangement, a nylon “type 11” internal pressure sheath is utilized as the inner layer. A reinforcement layer is provided around the internal pressure sheath. A polyurethane outer sheath is bonded thereto so as to provide waterproofing. End fittings are provided on each end of the thermoplastic hoses. The end fittings are typically crimped or swaged onto the hose. Connected to the end fittings on each of the ends of the hoses is a multiple quick-connect junction plate. This plate provides the connection plate between the subsea equipment and communication lines. It is usually installed using ROV unit subsea.
Steel flying leads presently being used define a collection of separate steel tubes bundled within a flexible vented plastic tube. Typically, a “Cobra” type end connection containing multiple quick-connect junction plate connections is provided at each end of the tubes. The individual tubes are routed into the respective end connections and welded into socket fitting in the opposing junction plate connections. These plates are usually installed by means of ROV units subsea.
One of the problems with the existing systems is that, while they are effective for small bores of less than two inches, they are extremely difficult to install with respect to large bore applications (bores of two inches or greater than two inches). For large bores, flexible or rigid pipe is used to transport or channel the fluid. In large bore applications, the large pressures involved tend to create greater separation pressures, i.e. pressures that separate the flowline from the equipment. As such, they would generally be ineffective in supporting the connection under the effect of great pressures. As such, a need has developed so as to provide a subsea flowline connection assembly which can be used for large bore applications and which can withstand the great pressures involved in such applications.
In the past, various patents have issued relating to subsea flowline connection assemblies. For example, U.S. Pat. No. 4,661,016, issued on Apr. 28, 1987 to Baugh et al., describes a subsea flowline connector for remotely connecting and releasing a first flowline to a complementary second flowline at a submerged location without the use of divers. Seals in the connector may be remotely replaced without the need to bring the connector to the surface. A bundle of control/supply lines are remotely connected to respective submerged lines at the same time as the flowline is connected.
U.S. Pat. No. 4,728,125, issued on Mar. 1, 1988 to B. J. Reneau, describes a grip-and-seal mechanically-locking flowline connector. In particular, flowlines have separately actuated gripping and sealing assemblies which are actuated by hydraulic pressure but are held in actuated positions using internally mounted mechanical-type mechanisms.
U.S. Pat. No. 5,593,249, issued on Jan. 14, 1997 to Cox et al., provides a diverless flowline connection system for connecting a flowline to a subsea wellhead or other subsea structure. The diverless flowline connection system is used with an ROV. The diverless flowline connection system includes a frame assembly having clamping arms for mounting the frame assembly to the flowline. A pair of winches are mounted to the frame assembly. Each winch includes a winch line for attachment to the wellhead to which the flowline is to be connected. Each winch is independently controlled so that the lateral position of the flowline may be variously adjusted by controlling each of the winches.
U.S. Pat. No. 5,807,027, issued on Sep. 15, 1998 to I. Ostergaard, shows a system for pull-in and interconnection of two pipelines in subsea position. A first pipeline is initially freely suspended. A second pipeline is mounted on a bottom-based manifold frame. The end section of the first pipeline is provided with a socket-like termination with a front end, which is provided with means for coupling of the terminator to complementary pipe coupling means on the second pipeline. The terminator is provided with a laterally-directed, longitudinally-shaped anchor member. The manifold frame is provided with receiving means for receipt and fixation of the anchor element. The anchor element and the receiving means are dimensioned and positioned such that when the anchor element is placed in position in the receiving means, the coupling means of the terminator will be positioned straight in front of the complementary coupling means on the second pipeline.
U.S. Pat. No. 6,805,382, issued on Oct. 19, 2004 to C. E. Jennings, describes a one-stroke soft-land flowline connector. A frame is used to land on a base and soft land a connector receptacle on the end of a flowline to a mandrel protruding from the base. After the frame lands on the base, the frame and the receptacle are pushed toward the base so as to cause frame latching members to latch the frame to the base. The frame holds the base and the receptacle above the mandrel. The frame and receptacle are pushed further towards the base and the connector receptacle abuts the mandrel. The connector receptacle moves relative to the frame as the frame is pushed closer to the base. This causes an actuator on the frame to move dogs on the receptacle to engage the mandrel and lock the receptacle to the mandrel.
U.S. Pat. No. 6,098,715, issued on Aug. 8, 2000 to Seixas et al., provides a flowline connection system having a pivotally-mounted funnel which is a permanent part of a subsea structure. The funnel is rotatably mounted so as to rotate from a vertical position to a horizontal position. Retractable pins engage a slot in the funnel to lock the funnel in a vertical position. This allows the funnel to rotate to the horizontal position to engage a hub connector. A flowline end termination stabs into the funnel while the funnel is in the vertical position. The flowline termination body has a flange connector on one end that connects to a flexible flowline.
U.S. Pat. No. 6,902,199, issued on Jun. 7, 2005 to Colyer et al., provides an ROV-activated subsea connector so as to connect a subsea flowline to a subsea connector hub. The connector has a frame with a tubular mandrel located within it. The mandrel connects to the flowline and has a forward end that engages the connector end. The mandrel moves axially relative to the frame between retracted and extended positions. A lock member on the forward end of the mandrel will engage the profile of the connector hub. An actuator mounted to the mandrel causes the lock member to move into engagement with the connector hub after the mandrel has been moved into engagement with the connector hub.
U.S. Pat. No. 7,112,009, issued on Sep. 26, 2006 to C. Mackinnon, provides an apparatus for substantially horizontal connection of a conduit to a subsea structure. A frame connectable to and supportable by the subsea structure. The frame has a docking device operable to allow a horizontal connection device to dock with the frame such that the frame is capable of bearing at least part of an operational load associated with the horizontal connection of the conduit to the subsea structure.
U.S. Patent Publication No. 2009/0283274, published on Nov. 19, 2009 to M. R. Lugo, discloses a connector assembly for connecting a hot stab to a hydraulic hose. The hot stab has a fluid conduit connector thereon. A hydraulic hose has a connector assembly at an end thereof suitable for joining to the fluid conduit connector of the hot stab. A sleeve is affixed to the hot stab and to the hydraulic hose so as to extend over and surround the fluid conduit connector and the connector assembly. A jam nut is affixed to the tubular portion of the fluid conduit connector. The sleeve is threadedly connected to the threaded exterior surface of the jam nut.
It is an object of the present invention to provide a subsea flowline connection system which is particularly configured to withstand the high pressures associated with large bore applications.
It is another object of the present invention to provide a subsea flowline connection system which facilitates the ability of an ROV to connect a fly-in connector to a flowline connector of the subsea structure.
It is still another object of the present invention to provide a subsea flowline connection system which allows the large bending moments from the flowline to be distributed over to the fixed part on the subsea structure.
It is still another object of the present invention to provide a subsea flowline connection system which effects a secure and strong seal between the fly-in connector and the flowline connector.
It is still another object of the present invention to provide a subsea flowline connection system which allows for flowline misalignment during the installation process.
These and other objects and advantages of the present invention will become apparent from a reading of the attached specification and appended claims.